Water removes heat from fire via evaporative cooling which in turn creates steam. Atomized water, in the physical state of steam/mist, starves a fire of oxygen and ensures that combustion or ignition cannot be sustained. When substrates adjacent to fire are saturated with water, a fire must provide enough heat to evaporate the water from the substrate before the substrate combusts.
The advantages of using water as an evaporative cooling agent against fire are its high heat absorbing capacity, a lack of toxicity, low cost and relatively good availability. However, a known disadvantage of water is its high fluidity. Water alone as a temporary suppressant against fire is inefficient due to excess run-off and an inability to sufficiently wet-out and absorb into high contact angle substrates. As such, significant manpower and time must be expended to re-soak high contact angle areas exposed to fire from which water has runoff or evaporated.
Prior Art Patents
U.S. Pat. No. 6,245,252 issued to Stockhausen GmbH & Co. KG teaches a cross-linked, water-swellable additive polymer in water/oil emulsion produced by an inverse phase polymerization reaction to be added to the firefighting water. This patent is directed to polymer systems and is deficient for the following reasons:
1. Although Acti-Quench is similar in functional concept to fire fighting foams and gels, such as these shown by Stockhausen, there is an important difference. Traditional “polymer shelled” gels depend on entrainment of water as a primary fire inhibitor. After the dissipation of all water from the polymer structures, the “polymer shells” constituting the structure is no longer useful as a fire barrier. In fact, without water the “polymer” is flammable.
2. Further, water-swellable polymers do not shear thin or exhibit pseudo-Thixotropic characteristics when used with standard fire fighting eduction systems.
3. Although water-swelling polymers are quite effective in creating a unique protective barrier, these polymeric systems are highly susceptible to UV sun-light destabilization.
4. Water-swelling polymer systems have a limited ambient storage range of 0–40° C.
5. Super absorbent polymers expand enormously and become extremely heavy in the process, thus, posing mechanical hazards due to clogging and the bursting of eduction equipment and in addition, the polymers have the potential for collapsing unstable structures due to the added weight of water.
6. Water-swelling polymers can only be effectively used with plain water. Highly valent contaminants such as detergents or ionic chemical salts disrupt the absorbency and heat resistant nature of water-swellable polymers thus causing a premature swelling and seizing of the polymer system.
U.S. Pat. No. 6,019,176 issued to Fire-Trol Holdings L.L.C., relates to “fire suppressant compositions, and methods of preparing and using such compositions consisting of: “water, at least about 5% by weight of a fire retardant salt and at least 1.5% by weight of ammonium thiosulfate along with other optional functional components such as corrosion inhibitors, suspending agents, coloring agents, antimicrobials and stabilizers.” This patent is deficient because said ammonia salt is highly corrosive to fire fighting equipment and has been proven to be environmentally toxic.
U.S. Pat. No. 5,518,638 to Buil et al discloses the use of Attapulgite and water-soluble salts for fire extinguishing formulations. This patent is deficient in not disclosing the purified Attapulgite clay covered in an embodiment of this invention and is also deficient in not showing the use of salts along with Attapulgite clay.
Additional Prior Art Patents
Dimanshteyn (U.S. Pat. No. 5,035,951) teaches alkali silicates and kaolin as fire-protectant materials.
Vandersall (U.S. Pat. No. 4,983,326) shows diammonium phosphate and diammonium sulfate to be fire-control agents.
Von Bonin et al (U.S. Pat. No. 5,709,821) teaches aluminum phosphate as a gel-former in fire protectant compositions. Specifically taught are gel formers comprising acid aluminum phosphate and a reaction product of boric acid and an alkanolamine, along with alkali metal compounds in the aluminum.
Hallo et al, U.S. Pat. No. 6,168,834 and U.S. Pat. No. 6,482,473 disclose compositions for dissipation of heat comprising a mineral clay, water and a surfactant. The compositions are used mainly to dissipate heat in welding and soldering processes.
Prior Art Reference
United Nations' website http://www.fao.org/docrep/q2570e/g2570eog.jpg makes mention of the use of attapulgite as a fire retardant at low concentrations.